Activated carbon blacks

ABSTRACT

Activated carbon blacks and the enhanced methods of preparing activated carbon blacks have been discovered. In order to form an activated carbon black, a conductive carbon black is coated with nanoparticles containing metal, and then catalytically activated in steam and an inert gas to form a catalytically activated mesoporous carbon black, where the mass of the catalytically activated carbon black is lower than the mass of the carbon black. The nanoparticles may serve as catalysts for activation rugosity of mesoporous carbon blacks. The catalytically activated carbon black material may be used in all manner of devices that contain carbon materials.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/080,021, filed on Jul. 11, 2008, titled “Activated Carbon Blacks,”and PCT/US2009/050084, filed on Jul. 9, 2010, titled “Activated CarbonBlacks,” the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to activated carbon blacks and to methodsfor their preparation. The activated carbons blacks may be used in allmanner of devices that may contain activated carbon materials, includingbut not limited to various electrochemical devices (e.g., capacitors,batteries, fuel cells, and the like), hydrogen storage devices,filtration devices, catalytic substrates, and the like.

BACKGROUND OF THE INVENTION

In many emerging technologies, such as electric vehicles and hybridsthereof, there exists a need for capacitors with both high energy andhigh power densities. Much research has been devoted to this area, butfor many practical applications such as hybrid electric vehicles, fuelcell powered vehicles, and electricity microgrids, the currenttechnology is marginal or unacceptable in performance and too high incost (See DOE Progress Report for Energy Storage Research andDevelopment fy2005 (January 2006) and Utility Scale Electricity Storageby Gyuk, manager of the Energy Storage Research Program, DOE (speaker 4,slides 13-15, Advanced Capacitors World Summit 2006)).

Electrochemical double layer capacitors (EDLCs, a form ofelectrochemical capacitor called an ultracapacitor, sometimes alsocalled a supercapacitor) are one type of capacitor technology that hasbeen studied for such applications. Electrochemical double layercapacitor designs rely on very large electrode surface areas, which areusually made from “nanoscale rough” metal oxides or activated carbonscoated on a current collector made of a good conductor such as aluminumor copper foil, to store charge by the physical separation of ions froma conducting electrolyte into a region known as the Helmholtz layer thatforms immediately adjacent to the electrode surface (see U.S. Pat. No.3,288,641). There is no distinct physical dielectric in an EDLC.Nonetheless, capacitance is still based on physical charge separationacross an electric field. The electrodes on each side of the cell andseparated by a porous membrane store identical but opposite ioniccharges at their surfaces within the double layer, with the electrolytesolution in effect becoming the opposite plate of a conventionalcapacitor for both electrodes.

Most EDLC devices are symmetric carbon/carbon electrodes made fromactivated carbon particulate powder. One consideration in designing anEDLC is its equivalent series resistance (ESR). While a theoreticallyperfect capacitor has an ESR of zero, a higher equivalent seriesresistance may result in power loss due to resistive heating of thecapacitor during charging or discharging. One method of lowering the ESRof the EDLC is to blend a small proportion of conductive carbon additivewith the active carbon prior to forming the electrodes. This conductiveadditive is typically a carbon black, such as Black Pearls 2000(available from Cabot Corp., Boston, Mass.) (see U.S. Pat. No.6,643,119), but may also be a finely powdered graphite (see U.S. Pat.No. 5,706,165). Alternatively, a vapor grown carbon fibril (see U.S.Pat. No. 6,288,888) or pulverized agglomerates of sintered vapor growncarbon fibrils (see U.S. Pat. No. 6,103,373) may also be utilized.

Conductive additives are usually very fine (small) particles compared tothe activated carbons they are blended with in order to enhanceconductivity. For example, the primary particle size of a typical carbonblack such as Vulcan XC72 (available from Cabot Corp., Boston, Mass.) orEnsaco 350G (available from Timcal Ltd., Bodio, Switzerland) is about 30nm in diameter, and carbon black primary particles typically form smallbonded aggregates varying up to a few hundreds of nanometers indimension. A typical activated carbon particle such as BP-20 (also soldas RP-20, available from Kuraray Chemical Co., Ltd., Osaka, Japan),varies from 3 μm to 30 μm in diameter, with a D₅₀ of 8 μm (see U.S. Pat.No. 6,643,119). The conductive additives effectively “coat” the muchlarger activated carbon particles to enhance their overallparticle-to-particle conductivity by increasing their totalcarbon-carbon contact surface. The smaller conductive particles provideadditional conductive pathways between the larger particles. A preferredratio of average conductive additive particle size to average activatedcarbon particle size may range from 1:5000 to 1:2 (see U.S. Pat. No.7,268,995).

While conductive additives may lower the ESR of EDLC devices, conductiveadditives have other attributes that are undesirable in EDLCapplications. For example, typical conductive additives do notcontribute substantially to the overall capacitance of the EDLC.Activated carbons used in some EDLCs have specific capacitance rangingfrom about 80 F/g to 120 F/g. (see U.S. application Ser. No. 12/070,062,filed Feb. 14, 2008; see also P. Walmet, L. H. Hiltzik, E. D. Tolles, B.J. Craft and J. Muthu, MeadWestvaco, Charleston, S.C., USA,Electrochemical Performance of Activated Carbons Produced from RenewableResources, Proceedings of the 16th International Seminar on Double-LayerCapacitors and Hybrid Energy Storage Devices, 581-607 (Deerfield Beach,Fla., Dec. 4-6, 2006)). In contrast, the specific capacitance of typicalconductive additives is much lower. For example, Black Pearls 2000 has aspecific capacitance of only 70.5 F/g intetraethylammoniumtetrafluoroborate (TEA) in acetonitrile (AN)electrolyte (TEA/AN) (see Carbon 43: 1303-1310 (2005)). Ensaco 350G,another high surface conducive carbon black with a manufacturer'sspecified BET surface area of 770 m²/g, has a specific capacitance ofonly 67 F/g even after thermal activation (see Carbon 43: 1303-1310(2005)). Without thermal activation, the specific capacitance of Ensaco350G samples range between 54 F/g and 66 F/g in 1.8Mtriethylmethylammonium (TEMA) in propylene carbonate (PC) electrolyte(TEMA/PC). Other possible conductive additives have even lower specificcapacitance. For example, the specific capacitance of Vulcan XC 72 isonly 12.6 F/g (see Carbon 43: 1303-1310 (2005)). Therefore, to maximizegravimetric energy density, the amount of lower specific capacitanceconductive additive blended with an activated carbon is minimized to atmost a single digit percentage (see, for example U.S. Pat. No.6,643,119, where a range of 1%-5% is preferred).

Another challenge in reducing the ESR of EDLCs while maintaining energydensity is the void/volume ratio which results from polydisperse randompacking of activated carbon particles. A typical void/volume ratio of anactivated carbon is about 0.25 to 0.35 (see U.S. Pat. No. 6,103,373).Activated carbon particles are jagged and rough—technically, rugose, andirregular in shape so lacking sphericity). Thus, activated carbonparticles random pack much less densely than equivalent smooth spheres.The inefficiency of random packing may be partly overcome by providing apolydispersion of activated carbon particles with a wide range of sizes(see U.S. Pat. No. 6,643,119). Although smaller activated carbonparticles do pack into the voids between large activated carbonparticles, their greater number and irregular nature result in increasedgrain boundary interface resistance (see U.S. Pub. No. 2007/0178310; seee.g. Sea Park, Chengdu Liang, Dai Sheng, Nancy Dudney, David DePaoli,Mesoporous Carbon Materials as Electrodes for ElectrochemicalDouble-Layer Capacitor, Materials Research Society Symposium BB (MobileEnergy), Proceedings Volume 973E (Boston, Mass., Nov. 27-Dec. 1, 2006)).The increased grain boundary interface resistance contributes to ahigher ESR in an EDLC.

As a result, electrocarbon suppliers offer air-classified material fromwhich fines have been removed in order to lower ESR (see e.g., P.Walmet, L. H. Hiltzik, E. D. Tolles, B. J. Craft and J. Muthu,MeadWestvaco, Charleston, S.C., USA, Electrochemical Performance ofActivated Carbons Produced from Renewable Resources, Proceedings of the16th International Seminar on Double-Layer Capacitors and Hybrid EnergyStorage Devices, 581-607, 592 (Deerfield Beach, Fla., Dec. 4-6, 2006)).Thus, it is difficult to further increase electrode macrodensity (lowerthe void/volume ratio) without increasing ESR. Stated another way,increasing volumetric energy density comes at the expense of powerdensity, and in any event is limited by the natural packings ofirregular activated carbon materials having micron scale averagediameters.

A further outcome of the tradeoff between volumetric density and powerdensity, and the limitation of the natural packing of activated carbonparticles, is that the voids of the resulting activated carbon materialare filled with more costly electrolyte than is required to cover thesurface available for Helmholtz layer capacitance. In a typical device,sufficient electrolyte ions are available for full double layering ofaccessible carbon surfaces if the electrode particles are merely surfacewetted with a film to the depth of a few solvated ions. For example, acoating of electrolyte less than 400 nm thick is more than sufficient,since each solvated ion is less than 2 nm, and by the basic physics ofthe double layer, with a 400 nm thick film there are ([400 nm/2 nm]*0.5)ions of the correct species (cationic or anionic) for either of the twoelectrodes in a device, or about 100 times more than the carbon'sproximate exterior double layer can theoretically accommodate (see PCTApp. No. PCT/US2007/0178310). The necessary porous separator within theEDLC also contains electrolyte, but itself contributes no capacitance.Thus, the porous separator represents an additional reservoir ofelectrolyte. Organic electrolyte is the single most expensive componentof a typical ultracapacitor. Moreover, surplus electrolyte addssubstantial cost and weight without enhancing capacitance.

It is desirable to tailor the electrode void/volume ratio to optimizecell performance (energy density and/or power density) while minimizingcost. The present means to do so are limited (see U.S. Pat. No.7,268,995).

BRIEF SUMMARY OF THE INVENTION

The scope of the present invention is defined solely by the appendedclaims, and is not affected to any degree by the statements within thissummary.

In order to address these issues, there is a need for a conductivecarbon additive with increased specific capacitance, that may beutilized to reduce the ESR of EDLCs, and that may improve volumetricenergy density without lowering power density.

In one embodiment, there method of forming an activated carbon black. Acarbon black is coated with nanoparticles. The carbon black is thencatalytically activated in steam and an inert gas to form acatalytically activated carbon black. The mass of the catalyticallyactivated carbon black is lower than the mass of the carbon black, andthe activated carbon black is mesoporous. In one embodiment, the totalmass loss of the carbon black after catalytic activation is greater thanabout 50%. In another embodiment, the activated carbon black has aspecific capacitance of at least 80 F/g. In yet another embodiment, theactivated carbon black has a specific capacitance of at least 110 F/g.In one embodiment, the carbon black comprises aggregates having at leastone dimension of less than 1000 nanometers. In one embodiment, thenanoparticles comprise a metal or oxides thereof. In yet anotherembodiment, the nanoparticles comprise iron, nickel, zirconium, cobalt,titanium, ruthenium, osmium, rhodium, iridium, yttrium, palladiumplatinum, or combinations thereof or alloys thereof. In one embodiment,the nanoparticles comprise at least two metal oxides.

In another embodiment, there is a device containing an activated carbon,and a carbon black. In one embodiment, the specific capacitance of theactivated carbon black is greater than 80 F/g, and in anotherembodiment, the specific capacitance of the activated carbon is alsogreater than 80 F/g. In another embodiment, the device is anelectrochemical device, a capacitor, a hydrogen storage device, afiltration device, or a catalytic substrate. In one embodiment, theproportion of activated carbon to activated carbon black is less than10:1.

In one embodiment, there is a device comprising an activated carbonblack with specific capacitance greater than 80 F/g. In anotherembodiment, the device is an electrochemical device, a capacitor, ahydrogen storage device, a filtration device, or a catalytic substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples steam activated for 30 and 60minutes.

FIG. 2 is a graph showing a voltage versus time constant current chargedischarge test of a carbon black sample compared with carbon blacksamples steam activated for 30 and 60 minutes.

FIG. 3 is a graph comparing discharge capacitance of a carbon black withcarbon black samples steam activated for 30 and 60 minutes, and carbonblack samples coated with nickel acetylacetonate, or ironacetylacetonate followed by steam activation for 30 and 60 minutes, andcarbon black samples coated with varying concentrations of zirconiumacetylacetonate, followed by steam activation for 60 minutes.

FIG. 4 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples coated with nickel acetylacetonatefollowed by steam activation for 30 and 60 minutes.

FIG. 5 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples coated with iron acetylacetonatefollowed by steam activation for 30 and 60 minutes.

FIG. 6 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples coated with zirconium acetylacetonateof varying concentration, followed by steam activation for 60 minutes.

FIG. 7 is a graph showing cyclic voltammograms of a carbon black samplecoated with iron acetylacetonate followed by steam activation for 60minutes.

FIG. 8 is a graph showing a cyclic voltammogram of an activated carbonblended with graphite, compared with an activated carbon blended with anactivated carbon black.

DETAILED DESCRIPTION OF THE INVENTION

Activation of conductive carbon blacks utilizing methods of engineerednanoparticle deposition has been discovered and is described herein. Theactivated carbon blacks may be utilized in ELDCs to reduce ESR, improvevolumetric energy density without lowering power density, and reduce theamount of surplus electrolyte used.

Previous patent applications by these inventors increased a carbon'susable surface by activation processes including surface coatedcatalytic nanoparticles. Specifically, general nanoparticle catalyticactivation methods enhancing the rugosity and proximate exterior ofcarbon materials have been described in U.S. patent application Ser. No.11/211,894, filed Aug. 5, 2005, and U.S. patent application Ser. No.12/070,062, filed Feb. 14, 2008, the entire contents of each areincorporated herein by reference, except that in the event of anyinconsistent disclosure or definition from the present application, thedisclosure or definition herein shall be deemed to prevail.

These nanoparticle catalytic activation processes may also be used toactivate a wide range of conductive carbon blacks, such as carbon blacksused typically as conductive additives in EDLCs. The use of activatedconductive carbon blacks in ELDCs may overcome several tradeoffsassociated with utilizing carbon blacks in EDLCs. Activated conductivecarbon black additives may have the same or greater specific capacitancethan the activated carbons they are blended with to construct an EDLC.Thus, gravimetric capacitance may not decrease as the proportion ofactivated conductive carbon black used in the EDLC is increased.

Moreover, because of relatively smaller size of conductive/capacitiveactivated carbon black particles compared with activated carbonparticles, the activated carbon black particles may be added inarbitrary amounts to intentionally fill voids in activated carbonmaterial, thereby reducing the void/volume ratio of an electrode to anydesired optimum without increasing ESR or decreasing gravimetric energydensity. By filling voids with activated carbon black material, it maybe possible to increase volumetric energy density and also reduce thequantity of electrolyte that fills voids but which is otherwise morethan is required for Helmholtz layer capacitance. Thus, activated carbonblacks may simultaneously increase conductivity, increase volumetricenergy density, and reduce surplus electrolyte.

Throughout this description and in the appended claims, the followingdefinitions are to be understood:

DEFINITIONS

The term “rugosity” used in reference to carbons refers to thedifference between actual surface area and theoretical geometric area inaccordance with the definition in the IUPAC Compendium of ChemicalTerminology, 2^(nd) edition (1997). For example, the sand side of asheet of ordinary sandpaper has substantially higher rugosity than thepaper side.

The term “particle” used in reference to precursors and activatedcarbons refers to a distribution of materials conventionally from about1 micron to more than 100 microns in diameter. Such particles can beconventionally prepared prior to and/or after physical or chemicalactivation, as described, for example, in U.S. Pat. No. 5,877,935, U.S.Pat. No. 6,643,119 and U.S. Pat. No. 7,214,646.

The term “carbon black” used in reference to carbon blacks and activatedcarbon blacks refers to a colloidal carbon material in the form ofapproximate spheres and of their fused aggregates with sizes below 1000nm, where a colloidal carbon is a particulate carbon with particle sizesbelow ca. 1000 nm in at least one dimension, according to the IUPACCompendium of Chemical Terminology, 2^(nd) edition, 1997.

The term “carbon black particle” used in reference to carbon blacks andactivated carbon blacks refers to a distribution of fused aggregatesconventionally below ca. 1000 nm in at least one dimension.

The phrase “fiber” used in reference to polymers and carbons refers tofilamentous material of fine diameter, such as diameters less than about20 microns, and preferably less than about 10 microns. Such fibers canbe obtained using conventional solvent or melt spinning processes or byunconventional spinning processes such as electrospinning. Such fibers,when fragmented into short pieces (as with conventional ‘milled’ carbonfiber at about 150 microns length with aspect ratios of 15 to 30 fromfiber diameters conventionally at least 7 microns), as used herein alsocomprise ‘particles’.

The term “mesoporous” as used in reference to a carbon describes adistribution of pore sizes wherein at least about 20% of the total porevolume has a size from about 2 nm to about 50 nm in accordance with thestandard IUPAC definition.

The phrase “catalytically activated” as used in reference to a carbonrefers to its porous surface wherein mesopores have been formed from theexternal surface of the carbon black particle, carbon particle, orcarbon fiber toward the interior by a catalytically controlleddifferential activation (e.g., etching) process. In some embodiments,metal and/or metal oxide particles of a chosen average size serve assuitable catalysts and a least a portion of the metal oxides remain inor on the carbon after the activation process.

The phrase “nanoparticle” as used in reference to catalytic particlesmeans a nanoscale material with an average particle diameter greaterthan 2 nm and less than 100 nm.

There are a variety of design considerations when manufacturing anactivated carbon for use in an EDLC. One factor is the grain boundaryresistance of the activated carbon material. As grain boundaryresistance increases, the equivalent series resistance (ESR) of theresulting EDLC using the activated carbon may also increase. One methodof lowering the grain boundary resistance, and thus the equivalentseries resistance (ESR) of the EDLC, is to blend a small proportion ofconductive carbon additive, such as a carbon black, with the activecarbon prior to forming the electrodes.

FIG. 1 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples that are steam activated for 30 and60 minutes at 900° C. In one embodiment, during the steam activation,nitrogen is flowed through the furnace to purge or remove air. Thenitrogen purge continues as the water is injected into the furnace. Thewater is introduced into the furnace using a metering pump. The nitrogenflow rate is held at about 200 mL/min and the water injection rate isheld at approximately between 150 and 175 mL/h. This steam activationmay also be referred to as 30% steam activation, where 30% is theapproximate molecular weight fraction of water (steam) flowed throughthe furnace as a proportion of the total gas flow.

As shown in FIG. 1, Ensaco 350G, a high surface conducive carbon blackwith a manufacturer's specified BET surface area of 770 m²/g (andmeasured BET surface between 650-790 m²/g), has a specific capacitanceof only 54 F/g in 1.8M triethylmethylammonium tetrafluoroborate(TEMABF₄) in propylene carbonate (PC) electrolyte, as shown in FIG. 1.Thermal activation does not significantly improve specific capacitance.After 30 minutes of activation in steam at 900° C., the specificcapacitance of the Ensaco 350G sample improves to 59.8 F/g in 1.8MTEMABF₄ in PC electrolyte. The measured specific capacitance of anotherEnsaco 350G sample activated for 60 minutes in steam at 900° C. is 66F/g in 1.8M TEMABF₄ in PC electrolyte. This result for 60 minutes ofactivation of Ensaco 350G in steam is similar to a 67 F/g resultreported in Carbon 43: 1303-1310 (2005) for an Ensaco 350G sampleactivated under other physical conditions.

FIG. 2 is a graph showing a voltage versus time constant currentcharge/discharge test of a carbon black sample compared with carbonblack samples that are steam activated for 30 and 60 minutes followingthe same steam activation procedure described in the text accompanyingFIG. 1.

A current charge/discharge test may be utilized to determine thedischarge capacitance of a sample, and may provide a more accuratepicture of how a device will operate. In an actual application, thecapacitor may be charged and discharged at constant current to a givenvoltage. The resistive voltage drop can be measured directly from thedata, and the waveforms typically have a linear slope (linearcharge/discharge profile) for pure electrical double layer chargestorage. Discharge capacitance may be determined from the current loadused in the experiment, mass of the sample, and the slope of thewaveforms using the following formula:

i=C(dv/dt)

In the formula, “i” is the current, C is the capacitance of the sample,and dv/dt is the change in voltage divided by the change in time. Asshown in FIG. 2, Ensaco 350G has a discharge capacitance of only 46.5F/g in 1.8M TEMABF₄ in PC electrolyte. After 30 minutes of activation insteam at 900° C., the discharge capacitance of the Ensaco 350G sampleimproves to 55.8 F/g in 1.8M TEMABF₄ in PC electrolyte. The measureddischarge capacitance of another Ensaco 350G sample activated for 60minutes in steam at 900° C. is 72.2 F/g in 1.8M TEMABF₄ in PCelectrolyte.

The specific capacitance (and thus discharge capacitance) of Ensaco 350Gmay be lower than the specific capacitance of many activated carbonmaterials utilized in ELDCs. For example, some activated carbons havespecific capacitance ranging from about 80 F/g to 120 F/g (see U.S.application Ser. No. 12/070,062, filed Feb. 14, 2008; see also P.Walmet, L. H. Hiltzik, E. D. Tolles, B. J. Craft and J. Muthu,MeadWestvaco, Charleston, S.C., USA, Electrochemical Performance ofActivated Carbons Produced from Renewable Resources, Proceedings of the16th International Seminar on Double-Layer Capacitors and Hybrid EnergyStorage Devices, 581-607 (Deerfield Beach, Fla., Dec. 4-6, 2006)). Thegravimetric capacitance of an activated carbon combined with Ensaco350G, as supplied by the manufacturer, or thermally activated, is lowerthan the gravimetric capacitance of the activated carbon. Thus, withoutan activation technique to improve the specific capacitance of carbonblack material, the proportion of carbon black used in an EDLC should beabout the minimum required to reduce ESR to a desired value, asincreased proportions of carbon black lower the gravimetric energydensity of an EDLC.

Previous patent applications by these inventors increased a carbon'susable surface, and thus, its specific capacitance, by activationprocesses including surface coated catalytic nanoparticles.Specifically, general nanoparticle catalytic activation methodsenhancing the rugosity and proximate exterior of carbon materials havebeen described in U.S. patent application Ser. No. 11/211,894, filedAug. 5, 2005, and U.S. patent application Ser. No. 12/070,062, filedFeb. 14, 2008. Similar techniques may be utilized to increase the usablesurface, and thus, the specific capacitance, of a carbon black.

In some embodiments, a metal-containing material, such as a metal oxidenanoparticle or a precursor thereto, is introduced during one or more ofthe processing stages to provide catalytic surface sites for thesubsequent etching of surface pores during the activating stage and/orto provide a desired electrochemical activity. The metal or metals ofthe metal containing materials are selected based on their catalyticand/or electrochemical activities.

In some embodiments, the nanoparticles have diameters of up to andincluding about 50 nm, in other embodiments, up to and including about15 nm, in other embodiments, up to and including about 8 nm, in otherembodiments, up to and including about 4 nm, and in other embodiments,about 2 nm. The preferred nanoparticle size mode will depend on thechoice of electrolyte and the device requirements, and the typical sizeof an individual carbon black particle or carbon particle that thenanoparticles are being deposited on. For example power density maypreferably have larger surface mesopores to reduce diffusion andmigration hindrance and local depletion, at the expense of less totalsurface and lower energy density.

It is generally accepted that EDLC pore size should be at least about1-2 nm for an aqueous electrolyte or about 2-3 nm for an organicelectrolyte to accommodate the solvation spheres of the respectiveelectrolyte ions in order for the pores to contribute surface availablefor Helmholtz layer capacitance. Pores also should be open to thesurface for electrolyte exposure and wetting, rather than closed andinternal. At the same time, the more total open pores there are justabove this threshold size the better, as this maximally increases totalsurface area. Substantially larger pores are undesirable because theycomparatively decrease total available surface.

In some embodiments, the metal and/or metal oxide nanoparticles compriseiron, nickel, zirconium, cobalt, titanium, ruthenium, osmium, rhodium,iridium, yttrium, palladium, or platinum, or combinations thereof, oralloys thereof. In some embodiments, the metal/oxide nanoparticlescomprise nickel oxide. In some embodiments, the metal/oxidenanoparticles comprise iron oxide. In some embodiments, thenanoparticles comprise alloys of nickel, iron, and zirconium.

Carbon black mesoporosity and total surface resulting from catalyticnanoparticle activation is a function of metal or metal oxide type(catalytic potency), nanoparticle size, nanoparticle loading (i.e. thecoverage on the carbon black, the number of nanoparticles per unitcarbon black exterior surface), carbon precursor, and carbon blackactivation conditions such as temperature, etchant gas (i.e. steam orcarbon dioxide or air) content as a percentage of the neutral (e.g.nitrogen) atmosphere, and duration of activation.

A metal-containing material may be introduced using an organometallicmetal oxide precursor or a mixture of such precursors. In oneembodiment, the metal oxide precursor preferably comprises a metalacetylacetonate, such as nickel acetylacetonate, iron acetylacetonate,or zirconium acetylacetonate. In another example, the metal oxideprecursor comprises metal acetate with an alcohol as a solvent, such asnickel acetate.

FIG. 3 is a graph comparing discharge capacitance of a carbon black withcarbon black samples steam activated for 30 and 60 minutes, and carbonblack samples coated with nickel acetylacetonate, or ironacetylacetonate followed by steam activation for 30 and 60 minutes, andcarbon black samples coated with varying concentrations of zirconiumacetylacetonate, followed by steam activation for 60 minutes.

In the experiment, nanoparticles are formed by solvent deposition of0.25% (metal:carbon weight) metal (iron or nickel) acetylacetonatedissolved in tetrahydrofuran (THF) onto the Ensaco 350G carbon blacksamples, followed by evaporation of the solvent and then metal oxidenanoparticle and catalytic mesopore formation using a steam activationat 900° C. for 30 or 60 minutes. The experiment nanoparticles are formedby solvent deposition of 0.125% or 0.25% (metal:carbon weight) metal(zirconium) acetylacetonate dissolved in tetrahydrofuran (THF) onto theEnsaco 350G carbon black samples, followed by evaporation of the solventand then metal oxide nanoparticle and catalytic mesopore formation usinga steam activation at 900° C. 60 minutes. In one embodiment, during thesteam activation, nitrogen is flowed through the furnace to purge orremove air. The nitrogen purge continues as the water is injected intothe furnace. The water is introduced into the furnace using a meteringpump. The nitrogen flow rate is held at about 200 mL/min and the waterinjection rate is held at approximately between 150 and 175 mL/h. Thissteam activation may also be referred to as 30% steam activation, where30% is the approximate molecular weight fraction of water (steam) flowedthrough the furnace as a proportion of the total gas flow.

These results are compared with a sample of Ensaco 350G as deliveredfrom the manufacturer (no activation), and Ensaco 350G samples activatedin steam at 900° C. for 30 and 60 minutes, as performed in theexperiments described in the text accompanying FIGS. 1 and 2. Acomparison of the measured discharge capacitance is shown in FIG. 3 andTable 1.

TABLE 1 Discharge Capacitance (F/g) Discharge Rate mA/g Sample 500 10001500 2000 2500 Average Ensaco 350G 46.5 41.3 39.6 39.4 38.0 40.9 Ensaco350G, 55.8 56.2 55.9 55.8 55.9 55.9 30 min. Steam at 900° C. Ensaco350G, 60 72.2 71.6 70.5 70.4 70.2 71.0 min. Steam at 900° C. Ensaco350G, 64.5 64.5 63.8 63.5 62.9 63.8 0.25% Fe(acac)₃, 30 min. Steam at900° C. Ensaco 350G, 90.2 87.4 85.5 84.7 83.5 86.3 0.25% Fe(acac)₃, 60min. Steam at 900° C. Ensaco 350G, 80.6 80.9 80.2 80.5 79.6 80.4 0.25%Ni(acac)₂, 30 min. Steam at 900° C. Ensaco 350G, 81.8 84.0 83.8 83.984.0 83.5 0.25% Ni(acac)₂, 60 min. Steam at 900° C. Ensaco 350G, 82.382.5 82.4 81.7 81.6 82.1 0.125% Zr(acac)₄, 60 min. Steam at 900° C.Ensaco 350G, 100.5 99.5 98.7 98.9 98.1 99.1 0.25% Zr(acac)₄, 60 min.Steam at 900° C.

Comparison of the average discharge capacitance results shows thatactivation of conductive carbon blacks utilizing methods of engineerednanoparticle deposition produces activated carbon blacks withsubstantially higher discharge capacitance (and hence, specificcapacitance) than non-activated or steam activated carbon black samples.Further, the average discharge capacitance of the activated carbon blacksamples is comparable to the discharge capacitance of activated carbons.

While the average discharge capacitance may indicate that activationusing various types of metal nanoparticles produces similar results,other factors may be considered when determining the process utilized tomanufacture an activated carbon black. For example, the reactivity ofthe nanoparticles deposited may affect mass loss caused by theactivation, as illustrated in Table 5 and the accompanying text. In theexperiments summarized in FIG. 3 and Table 1, carbon black mass loss fornickel nanoparticle activation is greater than carbon black mass lossfor iron nanoparticle activation, because the nickel nanoparticles aremore reactive. Mass loss associated with activation increases the costper kilogram of manufacturing an activated carbon black. Thus,activation using deposited iron nanoparticles may be more cost effectiveand may produce a similar specific capacitance result. On the otherhand, if a metal-containing material is not reactive enough, the timerequired to activate a carbon black (and thus manufacture the activatedcarbon black) may increase, thereby increasing the cost per kilogram.

The cost of the metal-containing materials used to provide catalyticsurface sites for surface pore etching during activation is anotherconsideration. If zirconium is less expensive than a similar quantity ofnickel, then the cost of a carbon black activated with nanoparticlescontaining zirconium may be comparatively cheaper than a carbon blackactivated with nanoparticles containing nickel. Further, the quantity ofmetal-containing materials used to provide catalytic surface sites forsurface pore etching during activation is yet another consideration. Forexample, Table 1 shows that a lower concentration (0.125%) of zirconiumacetylacetonate may result in an activated carbon black with similarspecific capacitance as a carbon black activated using a higherconcentration of nickel acetylacetonate. Using less metal-containingmaterial may reduce the cost of the manufactured activated carbon black.Other factors that may impact the choice of activation process includethe carbon black starting material and the electrolyte used in themanufactured capacitor.

As previously noted, carbon black mesoporosity and total surfaceresulting from catalytic nanoparticle activation is a function of manyfactors, including metal or metal oxide type, nanoparticle size,nanoparticle loading (i.e. the coverage on the carbon black, the numberof nanoparticles per unit carbon black exterior surface), carbonprecursor, and carbon black activation conditions such as temperature,etchant gas (i.e. steam or carbon dioxide or air) content as apercentage of the neutral (e.g. nitrogen) atmosphere, and duration ofactivation. Further, other activation processes, such as sequentialactivation processes disclosed in U.S. patent application Ser. No.12/070,062, may also be utilized to improve the mesoposity and totalsurface area of the activated carbon black. Some or all of these processparameters may be adjusted to produce activated carbon blacks withsimilar or enhanced characteristics as the embodiments described inTable 1 and FIG. 3.

FIG. 4 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples coated with nickel acetylacetonatefollowed by steam activation for 30 and 60 minutes. In one embodiment,nanoparticles of nickel are formed by solvent deposition of 0.25%(metal:carbon weight) nickel acetylacetonate dissolved intetrahydrofuran (THF) onto the Ensaco 350G carbon black samples,followed by evaporation of the solvent and then initial metal oxidenanoparticle and catalytic mesopore formation using a steam activationat 900° C. for 30 and 60 minutes. In one embodiment, during the steamactivation, nitrogen is flowed through the furnace to purge or removeair. The nitrogen purge continues as the water is injected into thefurnace. The water is introduced into the furnace using a metering pump.The nitrogen flow rate is held at about 200 mL/min and the waterinjection rate is held at approximately between 150 and 175 mL/h. Thissteam activation may also be referred to as 30% steam activation, where30% is the approximate molecular weight fraction of water (steam) flowedthrough the furnace as a proportion of the total gas flow. Specificcapacitance results for each sample as measured in using 1.8M TEMABF₄ inPC electrolyte are shown in Table 2.

TABLE 2 Ensaco 350G, Ensaco 350G, 0.25% Ni(acac)₂ 0.25% Ni(acac)₂ Ensaco350G, in THF, 30 min. in THF, 60 min. as received Steam at 900° C. Steamat 900° C. Specific 54.1 F/g 82.1 F/g  91.0 F/g Capacitance (1 V)Specific 60.0 F/g 92.8 F/g 103.4 F/g Capacitance (1.5 V)

Comparison of the specific capacitance results shows that activation ofconductive carbon blacks utilizing methods of engineered deposition ofnickel nanoparticles produces activated carbon blacks with substantiallyhigher specific capacitance than the non-activated (“as received”)carbon black samples.

FIG. 5 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples coated with iron acetylacetonatefollowed by steam activation for 30 and 60 minutes. In one embodiment,nanoparticles of iron are formed by solvent deposition of 0.25%(metal:carbon weight) iron acetylacetonate dissolved in tetrahydrofuran(THF) onto the Ensaco 350G carbon black samples, followed by evaporationof the solvent and then initial metal oxide nanoparticle and catalyticmesopore formation using a steam activation at 900° C. for 30 and 60minutes. In one embodiment, during the steam activation, nitrogen isflowed through the furnace to purge or remove air. The nitrogen purgecontinues as the water is injected into the furnace. The water isintroduced into the furnace using a metering pump. The nitrogen flowrate is held at about 200 mL/min and the water injection rate is held atapproximately between 150 and 175 mL/h. This steam activation may alsobe referred to as 30% steam activation, where 30% is the approximatemolecular weight fraction of water (steam) flowed through the furnace asa proportion of the total gas flow. Specific capacitance results foreach sample as measured in using 1.8M TEMABF₄ in PC electrolyte areshown in Table 3.

TABLE 3 Ensaco 350G, Ensaco 350G, 0.25% Fe(acac)₃ 0.25% Fe(acac)₃ Ensaco350G, in THF, 30 min. in THF, 60 min. as received Steam at 900° C. Steamat 900° C. Specific 54.1 F/g 69.6 F/g 83.0 F/g Capacitance (1 V)Specific 60.0 F/g 78.3 F/g 93.1 F/g Capacitance (1.5 V)

Comparison of the specific capacitance results shows that activation ofconductive carbon blacks utilizing methods of engineered deposition ofiron nanoparticles produces activated carbon blacks with substantiallyhigher specific capacitance than non-activated (“as received”) carbonblack samples.

FIG. 6 is a graph showing a cyclic voltammogram of a carbon blackcompared with carbon black samples coated with zirconium acetylacetonateof varying concentration, followed by steam activation for 60 minutes.In one embodiment, nanoparticles of zirconium are formed by solventdeposition of 0.125% or 0.25% (metal:carbon weight) zirconiumacetylacetonate dissolved in tetrahydrofuran (THF) onto the Ensaco 350Gcarbon black samples, followed by evaporation of the solvent and theninitial metal oxide nanoparticle and catalytic mesopore formation usinga steam activation at 900° C. for 60 minutes. In one embodiment, duringthe steam activation, nitrogen is flowed through the furnace to purge orremove air. The nitrogen purge continues as the water is injected intothe furnace. The water is introduced into the furnace using a meteringpump. The nitrogen flow rate is held at about 200 mL/min and the waterinjection rate is held at approximately between 150 and 175 mL/h. Thissteam activation may also be referred to as 30% steam activation, where30% is the approximate molecular weight fraction of water (steam) flowedthrough the furnace as a proportion of the total gas flow. Specificcapacitance results for each sample as measured in using 1.8M TEMABF₄ inPC electrolyte are shown in Table 4.

TABLE 4 Ensaco 350G, Ensaco 350G, 0.125% Fe(acac)₃ 0.25% Fe(acac)₃Ensaco 350G, in THF, 60 min. in THF, 60 min. as received Steam at 900°C. Steam at 900° C. Specific 54.1 F/g 84.9 F/g  99.4 F/g Capacitance (1V) Specific 60.0 F/g 96.0 F/g 113.4 F/g Capacitance (1.5 V)

Comparison of the specific capacitance results shows that activation ofconductive carbon blacks utilizing methods of engineered deposition ofiron nanoparticles produces activated carbon blacks with substantiallyhigher specific capacitance than non-activated (“as received”) carbonblack samples.

Table 5 illustrates the changes in carbon black characteristics relevantto EDLCs, caused by activation of a carbon black utilizing methods ofengineered nanoparticle deposition. Pore volume and distribution valuesare obtained using a standard nitrogen gas adsorption instrument.Specific surface area is calculated using the DFT (Density FunctionalTheory) method.

TABLE 5 Ensaco 350G, Ensaco 350G, 0.25% Fe(acac)₃ 0.25% Zr(acac)₄ Ensaco350G, in THF, 60 min. in THF, 60 min. as received Steam at 900° C. Steamat 900° C. Wt. loss (%) n/a 58.8 84.0 S_(DFT) (m²/g) 643 1013 1508 TotalPore 1.022 2.040 2.1015 Volume (cm³/g) Pore Size 70 49.8 6.9Distribution: micropore (%) Pore Size 30 50.2 75.9 Distribution:mesopore (%) Pore Size 0 0 17.2 Distribution: macropore (%)

As shown in Table 5, catalytic nanoparticle activation of an Ensaco 350Gcarbon black increases specific surface area (S_(DFT)) by over 50%,approximately doubles pore volume, and increases the percentage ofuseful mesopores for Helmholtz layer capacitance. Each of these changesmay contribute to the improved specific capacitance results observed inthe experiments described in FIGS. 3-6 and the accompanyingdescriptions. Comparison of the results shown in Table 5 and thedischarge capacitance shown in Table 1 further demonstrates that theselected action process impacts the properties of the manufacturedactivated carbon black.

Table 5 also shows substantial mass loss due to activation of the Ensaco350G carbon black material. The activation mass loss may vary dependingon the metal acetylacetonate species used (such as nickel, iron, orzirconium), the carbon black material, and the activation conditions. Inanother experiment not shown in Table 5, nanoparticles of nickel areformed by solvent deposition of 0.25% (metal:carbon weight) nickelacetylacetonate dissolved in tetrahydrofuran (THF) onto Ensaco 350Gcarbon black samples, followed by evaporation of the solvent and theninitial metal oxide nanoparticle and catalytic mesopore formation usinga steam activation at 900° C. for 60 minutes. In this experiment,average mass loss was 81.6%, which is substantially greater than the58.8% mass loss associated with the iron acetylacetonate activationexperiment shown in Table 5. Therefore, while the specific capacitanceof the resulting activated carbon material may be a consideration, thecost per kilogram of activated carbon black may be an additional designconsideration. Mass loss associated with activation increases the costper kilogram of manufacturing an activated carbon black.

Other carbon black starting materials may be activated using utilizingsimilar methods of engineered deposition of metal nanoparticles, withcomparable or improved results. FIG. 7 is a graph showing cyclicvoltammograms of a carbon black sample coated with iron acetylacetonate,followed by steam activation for 60 minutes. In one embodiment,nanoparticles of iron are formed by solvent deposition of 0.25%(metal:carbon weight) iron acetylacetonate dissolved in tetrahydrofuran(THF) onto a sample of Black Pearls 2000, followed by evaporation of thesolvent and then initial metal oxide nanoparticle and catalytic mesoporeformation using a steam activation at 900° C. for 60 minutes. In oneembodiment, during the steam activation, nitrogen is flowed through thefurnace to purge or remove air. The nitrogen purge continues as thewater is injected into the furnace. The water is introduced into thefurnace using a metering pump. The nitrogen flow rate is held at about200 mL/min and the water injection rate is held at approximately between150 and 175 mL/h. This steam activation may also be referred to as 30%steam activation, where 30% is the approximate molecular weight fractionof water (steam) flowed through the furnace as a proportion of the totalgas flow. The mass loss associated with the activation is about 79%.

In one embodiment, a sample electrode is formed comprising 94 wt. %activated carbon black, 3 wt. % KS6 graphite, and 3 wt. % Teflon PTFE 6Cbinder. (Teflon PTFE 6C is available from DuPont Corporation,Wilmington, Del.) The specific capacitance of the sample as shown inFIG. 7 is 102.8 F/g at 1.0 V, and 110.6 F/g at 1.5 V, as measured in1.8M TEMABF₄ in PC electrolyte. In comparison, non-activated BlackPearls 2000 has a specific capacitance of only 70.5 F/g in TEA/ANelectrolyte. The increase in specific capacitance is generallyattributable to the activation of the carbon black, and not thedifferent electrolyte utilized in the comparative example (see P.Walmet, L. H. Hiltzik, E. D. Tolles, B. J. Craft and J. Muthu,MeadWestvaco, Charleston, S.C., USA, Electrochemical Performance ofActivated Carbons Produced from Renewable Resources, Proceedings of the16th International Seminar on Double-Layer Capacitors and Hybrid EnergyStorage Devices, 581-607, 595 (slide 15) (Deerfield Beach, Fla., Dec.4-6, 2006), showing that the capacitance of several materials in TEMABF₄in PC electrolyte is approximately equal to the capacitance of the samematerials in TEA/AN electrolyte).

The KS6 graphite in this embodiment may contribute to a reduced ESR, butan electrode may not require KS6 graphite, because carbon black oractivated carbon black may be utilized to reduce ESR. Therefore, inanother embodiment, an electrode may be formed utilizing a lowerpercentage of graphite. In yet another embodiment, an electrode may beformed using no graphite.

Activated carbon blacks may also be combined with activated carbons toform electrodes. FIG. 8 is a graph showing a cyclic voltammogram of anactivated carbon blended with graphite, compared with an activatedcarbon blended with an activated carbon black.

In one experiment, ordinary (inexpensive) commercial MeadWestvacoNuchar® chemically activated filtration carbon (available fromMeadWestvaco Corporation, Covington, Va.) is steam activated at 850° C.for 30 minutes. During the steam activation, nitrogen is flowed throughthe furnace to purge or remove air. The nitrogen purge continues as thewater is injected into the furnace. The water is introduced into thefurnace using a metering pump. The nitrogen flow rate is held at about200 mL/min and the water injection rate is held at approximately between150 and 175 mL/h. This steam activation may also be referred to as 30%steam activation, where 30% is the approximate molecular weight fractionof water (steam) flowed through the furnace as a proportion of the totalgas flow.

Ensaco 350G carbon black is activated by solvent deposition of 0.25%(metal:carbon weight) iron acetylacetonate dissolved in tetrahydrofuran(THF) onto a sample of Ensaco 350G, followed by evaporation of thesolvent and then initial metal oxide nanoparticle and catalytic mesoporeformation using a steam activation at 900° C. for 60 minutes. A firstelectrode is formed utilizing 92 wt. % activated Nuchar, 5 wt. % KS6graphite, and 3 wt. % Teflon PTFE 6C binder, and a second electrode isformed utilizing 92 wt. % activated Nuchar, 5 wt. % activated Ensaco350G, and 3 wt. % Teflon PTFE 6C binder. Specific capacitance resultsfor each sample electrode as measured in using 1.8M TEMABF₄ in PCelectrolyte are shown in Table 6.

TABLE 6 92% Activated Nuchar, 30 min. Steam at 850° C. 5% Ensaco 350G,92% Activated Nuchar, 0.25% Fe(acac)₃ 30 min. Steam at 850° C. in THF,60 min. 5% KS6 graphite Steam at 900° C. Specific  98.5 F/g 112.2 F/gCapacitance (1 V) Specific 107.2 F/g 123.6 F/g Capacitance (1.5 V)

The specific capacitance of KS6 graphite is approximately two orders ofmagnitude lower than the activated carbon in Table 6 (see F. Joho, M. E.Spahr, H. Wilhelm, P. Novak, The Correlation of the Irreversible ChargeLoss of Graphite Electrodes with their Double Layer Capacitance, PSIScientific Report 2000/Volume V, General Energy, 69-70, 70 (PaulScherrer Institut, March 2001), reporting 0.769 F/g specific capacitanceof KS6 graphite in 1M M LiPF₆, EC:DMC (1:1) electrolyte). This isconsistent with the relatively low BET surface area of KS6 graphite (20m²/g according to the manufacturer data sheet). Therefore, the increasein specific capacitance can be attributed to the use of activated carbonblack in the electrode. Similarly, an improvement in specificcapacitance of an activated carbon/carbon black electrode may beachieved by substituting an activated carbon black in place of a similarpercentage content of the non-activated carbon black.

In other embodiments, activated carbon blacks may be utilized inelectrodes containing other types of activated carbons formed from avariety of carbon and carbon precursor materials, such as Kynol fiberprecursor (available from American Kynol, Inc., Pleasantville, N.Y.).The carbon material may be activated utilizing other thermal activationor general nanoparticle catalytic activation methods, where thenanoparticle deposition on the carbon may be performed by techniquessuch as general solvent coating methods using organometallic precursorsfollowed by thermal decomposition into nanoparticles, orelectrodeposition as described in U.S. patent application Ser. No.12/118,413, filed May 9, 2008, the entire contents of each areincorporated herein by reference, except that in the event of anyinconsistent disclosure or definition from the present application, thedisclosure or definition herein shall be deemed to prevail.

Where an activated carbon black has equal or similar specificcapacitance to an activated carbon, the proportions of each utilized toform the electrode may be varied without negatively impactinggravimetric capacitance. Thus, the percentage of activated carbon blackmay be increased as necessary to lower ESR to a desired value, withoutreducing the gravimetric capacitance of the electrode.

Further, the proportion of activated carbon black may be increased inorder to fill voids in the activated carbon material, improvingvolumetric capacitance without negatively effecting gravimetriccapacitance. This may complement the use of pressure rolling anelectrode to reduce voids during the manufacturing process, or mayeliminate the need for pressure rolling altogether. Using activatedcarbon black to fill voids displaces surplus costly electrolyte that maybe unnecessary for Helmholtz layer capacitance, including ion mobility.In one embodiment, the approximate minimum quantity of electrolyte maybe determined by increasing the proportion of activated carbon black,and decreasing the amount of electrolyte utilized, until the specificcapacitance of an electrode begins to decrease. Utilizing thisexperiment, it is assumed that the decrease in specific capacitance isat least partially attributable to having insufficient electrolyte toform a Helmholtz layer on all of the carbon and carbon black surfacearea available. In another embodiment, the approximate minimum quantityof electrolyte may be determined by increasing the proportion ofactivated carbon black, and decreasing the amount of electrolyteutilized, until the measured ESR of an electrode begins to increase.Utilizing this experiment, it is assumed that the increase in ESR is atleast partially attributable to ion mobility being inhibited because ofinsufficient electrolyte solvent. In yet another embodiment, theapproximate minimum quantity of electrolyte may be determined byincreasing the proportion of activated carbon black, and decreasing theamount of electrolyte utilized, until the specific capacitance of anelectrode begins to decrease, or until the ESR of an electrode begins toincrease.

This invention discloses a novel conductive material created throughactivation of conductive carbon blacks utilizing methods of engineerednanoparticle deposition. The nanoparticles may serve as catalysts foractivation rugosity of carbon blacks. The activated carbon blackmaterial has specific capacitance significantly greater than thespecific capacitance of non-activated carbon black material. Moreover,because the specific capacitance of activated carbon blacks may be equalor comparable to the specific capacitance of many activated carbonmaterials, activated carbon blacks may be combined with activatedcarbons while partially or completely avoiding the gravimetriccapacitance penalty sometimes associated with adding non-activatedconductive carbon blacks to activated carbons when manufacturing EDLCs.Whereas typically less than 10% proportion of carbon black is utilizedin an EDLC in order to minimize the negative impact on gravimetriccapacitance, activated carbon blacks may be combined with activatedcarbon in far greater proportions. In one embodiment, an EDLC maycontain activated carbon black material, and no activated carbonmaterial.

In some embodiments, the volumetric capacitance of an activated carbonblack may be lower than the volumetric capacitance of an activatedcarbon. As a consequence, the volume of an EDLC containing activatedcarbon black material, and no activated carbon material, may be greaterthan the volume an EDLC (of equal charge storage capacity) containinghigher proportion of activated carbon. While greater volumetriccapacitance is desirable in many applications, there are someapplications where volumetric capacitance is a secondary designconsideration. In those applications, a higher proportion of activatedcarbon black may be utilized despite the increased volume of theresulting EDLC. For example, an EDLC containing activated carbon blackmaterial, and no activated carbon, may be utilized in some designapplications despite the lower volumetric capacitance of an activatedcarbon black material.

EDLCs are sometimes fabricated using a polydispersion of activatedcarbon particles with a wide range of sizes in order to fill the voidsintroduced by random packing of activated carbon particles. By fillingvoids with activated carbon material, volumetric capacitance may beincreased. However, as previously discussed, this technique may fillvoids at the expense of increased grain boundary resistance, and hence,increased ESR of the finished EDLC, and lower power density. As notedabove, activated carbon black material may be added in greaterproportions because of its improved specific capacitance. Hence,activated carbon black may be used to fill the voids commonly found inactivated carbons. By using activated carbon black material to fillvoids, the activated carbon material may be air-classified to reducefines, as a polydisperse distribution of activated carbon particle sizesmay no longer be as necessary in order to fill voids. Hence, byutilizing activated carbon black material to fill voids, volumetricenergy density may be improved without sacrificing power density.

Electrolyte added to an EDLC during the manufacturing process may fillvoids in the activated carbon material. Any electrolyte used in an EDLCbeyond what is required to cover the surface available for Helmholtzlayer capacitance and facilitate ion mobility is surplus. By usingactivated carbon black to fill voids in activated carbon, surpluselectrolyte is displaced. Therefore, the amount of unnecessary surpluselectrolyte contained in an EDLC may be reduced by utilizing activatedcarbon blacks to fill voids. As an additional benefit, by filling voidswith activated carbon black material, volumetric capacitance isincreased. Experimentally, the amount of surplus electrolyte may bedetermined by increasing the volume of activated carbon black (anddecreasing the volume of electrolyte by the same amount) until thespecific capacitance of the manufactured EDLC decreases, where thedecrease in specific capacitance is assumed to be at least partiallyattributable to having insufficient electrolyte to form a Helmholtzlayer on all of the carbon and carbon black surface area available. Ifion mobility is inhibited by lack of electrolyte, ESR may increase.Therefore, the amount of surplus electrolyte may also be experimentallydetermined by increasing the volume of activated carbon black (anddecreasing the volume of electrolyte by the same amount), until the ESRof the manufactured ELDC stops decreasing and begins again to increase,attributable at least in part to insufficient solvent to permit facileion migration between the two electrodes.

Finally, activated carbon black material is still conductive, andtherefore, may be utilized to lower grain boundary resistance, andhence, the ESR of EDLCs. The activation process may increase the sheetresistivity of the activated carbon black because of the surfacerugosity and mesopores created, and therefore reduce the ability ofactivated carbon black to reduce ESR. However, the improved specificcapacitance of activated carbon black material allows an increasedproportion of activated carbon black to be added in order to offset thiseffect (if any). As stated before, depending on the specific capacitanceof the activated carbon and activated carbon black material, adding moreactivated carbon black may have little or no negative effect on thegravimetric capacitance of the EDLC.

The catalytically activated carbon black material may be used in allmanner of devices that contain carbon or carbon black materials,including various electrochemical devices (e.g., capacitors, batteries,fuel cells, and the like), hydrogen storage devices, filtration devices,catalytic substrates, and the like.

The foregoing detailed description has been provided by way ofexplanation and illustration, and is not intended to limit the scope ofthe appended claims. Many variations in the presently preferredembodiments illustrated herein will be apparent to one of ordinary skillin the art, and remain within the scope of the appended claims and theirequivalents.

1. A device, comprising: an activated carbon; and an activated carbonblack.
 2. The device of claim 1, wherein a proportion of activatedcarbon to activated carbon black is less than 10:1.
 3. The device ofclaim 1, wherein the device is an electrochemical device, a capacitor, ahydrogen storage device, a filtration device, or a catalytic substrate.4. The device of claim 1, wherein the device is a capacitor, theactivated carbon has a specific capacitance of at least 80 F/g, and theactivated carbon black has a specific capacitance of at least 80 F/g. 5.The device of claim 1, wherein the device is a capacitor, and a specificcapacitance of the activated carbon black is at least 80 F/g.
 6. Adevice, comprising: an activated carbon black, wherein a specificcapacitance of the activated carbon black is at least 80 F/g.
 7. Thedevice of claim 6, wherein the device is an electrochemical device, acapacitor, a hydrogen storage device, a filtration device, or acatalytic substrate.
 8. A method of forming an activated carbon blackcomprising: (a) providing a carbon black; (b) coating the carbon blackwith nanoparticles; and (c) catalytically activating the carbon black insteam and an inert gas to form a catalytically activated carbon black;wherein the mass of the catalytically activated carbon black is lowerthan the mass of the carbon black, and wherein the activated carbonblack is mesoporous.
 9. The method of claim 8, wherein the activatedcarbon black has a specific capacitance of at least 80 F/g.
 10. Themethod of claim 8, wherein the activated carbon black has a specificcapacitance of at least 110_F/g.
 11. The method of claim 8 wherein thecarbon black comprises aggregates having at least one dimension of lessthan 1000 nanometers.
 12. The method of claim 8, wherein thenanoparticles comprise a metal.
 13. The method of claim 8, wherein thenanoparticles comprise at least two different metal oxides.
 14. Themethod of claim 8, wherein the nanoparticles comprise iron, nickel,cobalt, titanium, ruthenium, osmium, rhodium, iridium, yttrium,palladium platinum, zirconium, or combinations thereof or alloysthereof.
 15. The method of claim 12 wherein the nanoparticles compriseiron, nickel, cobalt, titanium, ruthenium, osmium, rhodium, iridium,yttrium, palladium platinum, zirconium, or combinations thereof oralloys thereof.
 16. The method of claim 8, wherein a total mass loss ofthe carbon black after step c is greater than about 50%.
 17. A materialcomprising the activated carbon black made by the method of claim 8 anda binder.
 18. A device containing the activated carbon black of claim 8.19. A device containing the material of claim
 17. 20. The device ofclaim 19, wherein the device is an electrochemical device, a capacitor,a hydrogen storage device, a filtration device, or a catalyticsubstrate.